Process of forming bifocal lenses.



H. w. HILL. PROCESS OF FORMING BIFOCAL LENSES. APPLICATION FILED .IUNE 3,1914.

' 1 ,1 90,242. y Patented July 4, 1916.

PP/OR APT WITNESSES."

l/VI/E/VTOH HARRY W H/LL To all whom it may concern ng a make any HA-RRY'W. HIIiL, 0F SOUTHBRIDGE, MASSACHUSETTS, ASSIGNOR TO AMERICAN OPTICAL COMPANY, OF SOUTI-IBRIDQE, MASSACHUSETTS, A VOLUNTARY ASSO- CIATION OF MASSACHUSETTS.

rnoonss or FORMING nirocnri LENSES.

. Be it known that I, HARRY W. HILL, a citizen of the United States, residing at Southbridge, in the county of Worcester and State of Massachusetts, have invented certain new and useful Improvements in Processes of Forming Bifocal Lenses, of which the following is a specification.

My invention relates to improvements in bifocal lenses and has particular reference to an improved process for forming the same.

The leading object of my invention is the provision of an improved process for facilitating the satisfactory uniting of the segment and major portion of a two part bifo cal lens or the like.

A further object'of my invention the provision of an improved process for inexpensively and satisfactorily-uniting the sald parts which will reduce to a minimumboth strain in the lenses and liability of breakage thereof.

Another object of my invention is the provision of a separating member for the parts which shall be independent of both of the parts and which shall permanently unite therewith during the fusing operation and thus facilitate completion of the lens after fusion of the parts thereof.

Other objects and advantages of my 1mprovement should be readily apparent by. reference to the following description taken in connection with the accompanying drawand it will be understood that I may modifications in the specific de l tails of construction shown and described within the scope of the appended claims.

without departing from or exceeding the spirit of my invention.

Figure I represents a plan view of a blank illustrating the prior art process and being so designated. Fig. II represents a sectional view on the line II-II of Fig. I. Fig. III represents a plan View of one step in my improved process. Fig. IV represents a sectional view on the line IV-+ IV of r Fig. III. Fig. Vrepresents a plan view of the completed blank constructed by the use of my process. Fig. VI represents a sectional view on the line VI-VI of Fig. V.

In the drawings, in which similar characters of reference are employed to denote corresponding parts throughout the several Specification of Letters Patent.

Patented July 4., 1916.

Application filed iTune 3, 1914. Serial No. 842,576.

views, the numeral 1 designates the main or major portion of a lens blank having preferably formed therein the recess or countersink 2 adapted to receive a portion of the segment 3, the major-portion 1 and segment 3 being formed from glass or similar material having different lndices of refraction,"

whereby the same curve ground on the outer faces'of the major and minor portions of the lens will produce different powers in said two portions.

/PI101 to my invention it has been custom- .ary' in forming lenses of this character to rest one edge of the segment against the maj or portion of the lens and to place beneath the opposite edge thereof or at a plurality of points, as may be preferred, a block A of steel. The lens is then subjected to sufiior countersink 2, the member or members 4' cient heat 'to render the same plastic, this holding one edge up as long as possible so that the gas and air accumulated between the segment andthe face of thecountersink may be expelled at this side. The operation to this extent is quite desirable and advantageous. Great difficulty has been experienced, however, on account of the presence of the steel member 4, one great disad vantage of this member being readily evident by reference to Figs. Iand II, from which it will be seen that waves or distortions are occasioned as at 5 on account of the glass having to soften and flow around the member 4:. These consequentlydestroy the utility of the glass at this point and render it necessary to cut a much smaller lens from the blank than would otherwise be the case,

while rendering it absolutely impossible to provide a lens such as that indicated by the dotted lines on the blank in Fig. V, that is to say, one in which the reading portion is disposed toward the center and a distance portion is provided both above and below the segment.

Another great disadvantage of this prior art construction is the necessity for removal of the steel member before completion of the lens; this removal can only be done by in some way removing the steel member from between the two parts which are fused around it, thus'entailing in practically every instance chipping and breaklngofl' of the edge of the segment and of the major lens, further impairing the. utility of the blank so that ordinarily the useful portion of the blank is only about that indicated by. the dotted lines in Fig. I.

My improved construction and process of forming a bifocal lens blank, however, does away with all of these disadvantages, and makes it possible to produce a lens both without the wave effects and distortions present in the prior art blanks, and in all cases to at least reduce these defects to a negligible minimum and thus enables the cutting out of a lens such as indicated by the dotted lines in Fig. V, or if desired the forming of two lenses from a single blank,

' an impossibility with the prior art form of construction.

A further great advantage of my improve-- of having been chipped off or broken away,

this being both'an advantage in working the lens and reducing to a minimum liability of the expensive blank becoming broken in course of manufacture, as the blank is neither weakened by removal of of being stiff and rigid, thus eliminating en:

tirely or reducing to aminimum any pose the member 4 or'oracked in the attempt to remove the same.-

My invention consists in the use in the old process of a member or members 6 whlch are formed from glass or similar material which will fuse and unite with the parts to be joined and will become an integral part thereof. By this improved process I take the major lens, form the countersink therein, place in position my wedge or wedges of glass, and, then mount the minor portion or segment 3 of the lens in position as indicated in Fig. IV. Upon fusing the portion 6 while serving the function of a spacing mem-- ber as the segment is fused, eventually is softened and melts into the segment in place sible wave effect, such as indicated at 5 in Fig. I, while at the same time the fact that this member is of. glass. and united'with the parts permits after the fusing of the grinding of the lens without necessity of removing.

the spacing member and without damage to the grinding tools;

To further increasetheeificiency of my improved-processand to eliminate any pos sible slipping of the separating member, such as has proved itself objectionable in the 'case of the steel insert previously employed, 1 may if desired, place either on the lower blan or on my separating member a suitable adhesive which will serve to temporarily retain the separating member in position, thisadhesive however, being preferably such as to either be entirely dried ofi and evaporated by the fusing action or else such as to unite with the separating member and blanks .during the fusing action so that no trace of the same will be present in ing use of a separating member of the same material astheparts to be united, that it may in some instances be of some other material which will either evaporate or be practically or entirely eliminated by the heating action, one of the essentials of my process being the feature of so uniting the parts that in the finished condition there will be no pronounced separating member, no member which it is necessary to remove, and there will be no member which will cause the disagreeable and destructive wave of such which are caused by the steel member which has been in common use prior to my invention.

If desired, 1 may slightly modify my process by first cementing the separating member or members to the major lens at the desired point thereon and may anneal the said major blank by raising the tempera-- portion with a depression therein, mounting a spacing member having an adhesive coatmg at one side of the depression, mounting a second blank above the depression with one side held away from the first blank by the said spacing member, subjecting the said partsv to a welding heat, whereby one of the blanks is caused to .soften and settle down upon and unite with the spacing member and with the other blank, and grinding the resultant unitary blank into a; finished ophthalmic lens. a

2. The process of making bifocal lenses which consists in supporting the parts to be united inspaced relation through the medium of a spacing member of the same mater ial as the parts to be united, applying an adhesive to retain the spacing member in correct positlon between the parts, and subjecting the parts and spacing member to a weldmg heat to fuse the three parts into a cal lenses, which consists in forming a major single unitary structure, substantially as described.

3. The process of forming an ophthalmic bifocal lens blank, consisting in forming a major portion with a depression therein, coating a spacing member with a suitable adhesive, placing the spacing member at one side of the depression, mounting a second blank on the first with one edge in engagement with the first and the other spaced therefrom by the spacing member,' and subj ecting the parts to a welding heat, whereby the spacing member and one of the blanks are rendered plastic and settle down into close engagement with the other blank and 15 HARRY W. HILL.

Witnesses i JOSEPH J. DEMERs, H. K. PARSONS. 

